This invention relates to storing stem cells and phocytes without unacceptable loss of cell function.
Stem cells are undifferentiated cells which are pluripotent--i.e., they can differentiate into cells which have diverse functional characteristics. They are not fully differentiated, and they retain the ability to duplicate. Of particular interest are lymphohematopoietic stem cells which differentiate into lymphoid and myeloid cells. Lymphohematopoietic stem cells include the following cells, as well as many others: a) cells that are colony-forming cells for granulocytes/monocytes (CFU-GM); b) cells that are colony-forming for erythrocytes (BFU-E); c) colony-forming cells for eosinophiles (CFU-Eo); d) multipotent colony forming cells (CFU-GEMM); e) immature lymphoid precursor cells, including precursors of B-cells and T-cells; and f) pluripotent stem cells. FIG. 1 is a commercially distributed chart depicting the various cells including stem cells involved in hematopoiesis.
Stem cells are essential for transplantation, for example, bone marrow transplantation. Typically bone marrow transplants involve harvesting marrow cells, washing them with a buffer to remove undesired cells and material (e.g., T-cells and/or malignant cells), and suspending then in a suitable medium (e.g. RPMI, autologous serum, and DMSO). The resulting material is either immediately infused into the recipient or it is cryopreserved (frozen well below 0.degree. C.) for later use. Peripheral blood stem cells are also used for bone marrow transplantation. Stem cells are obtained from peripheral blood by leukapheresis, with similar subsequent processing.
Civin (U.S. Pat. Nos. 4,714,680; 4,965,204; and 5,035,994) describes a monoclonal antibody specific for an antigen on human pluripotent lymphohematopoietic stem cells, and not for antigens on normal mature human lymphoid and myeloid cells. Tsukamoto et al. (U.S. Pat. No. 5,061,620) describe human hematopoietic stem cells, their separation, characterization, and use. Each of those patents is hereby incorporated by reference. These and other rapidly advancing technologies may make bone marrow transplants and other medical procedures available to a far larger patient population than can currently receive this treatment.
The lymphocyte family includes lymphoid stem cells as well as the differentiated cells resulting from them (T-cells, B-cells, and plasma cells). See FIG. 1. In various situations, it is desirable to obtain cell populations enriched in certain lymphocytes and/or depleted in others. For example, it may be desirable to destroy a certain population of malignant or infected lymphocytes. Alternatively, it may be desirable to activate a patient's lymphocytes outside the body (e.g., with IL-2) and then to reinfuse them. In short, various technologies are known for treating and/or engineering stem cells or lymphocytes outside the body, and returning the treated cells to the body. Finally, for patients in remote locations, it may be necessary to ship lymphocytes to remote locations for histocompatibility testing in preparation for a transplant, requiring storage during shipment.
Various technologies are known for segregating or selectively enriching or destroying populations of lymphocytes or stem cells, in addition to the technologies mentioned above. For example, other techniques include the CEPRATE.TM. stem cell concentrator sold by CellPro, Inc. of Seattle, Wash., panning techniques, cell sorting (e.g. fluorescent antibody cell sorting (FACS)), and the use of magnetic beads.
There is a particular need for a convenient and effective way to store stem cells and/or lymphocytes after they are obtained (e.g., in the manner described by Tsukamoto et al.) and before they are used.